An energy recovery unit (ERU) captures waste energy—such as thermal heat or high-pressure hydraulic force—that would otherwise be exhausted into the environment and recycles it back into the active system to power incoming processes. In industrial water desalination, an energy recovery device captures the high-pressure energy from outgoing reject brine and transfers it directly to incoming raw seawater. In commercial building ventilation, an energy recovery ventilator (ERV) uses exhaust air to pre-condition the temperature and humidity of incoming fresh outdoor air, cutting heating and cooling loads.